Boat propeller

ABSTRACT

A ship propeller arrangement (1), in particular for motor boats, has a propeller being operated with super-cavitative rotating speed and having its propeller blades (5) provided with step bearings (7) being swivelable around threaded bolts (6), which are screwed into a propeller star (8) being put onto the propelling shaft (2). Rotation of each propeller blade (5) is effected by a hollow shaft (17) surrounding the propelling shaft (2) and by bevel gears (14, 15) being put onto the hollow shaft as well as onto the propelling shaft and being in meshing engagement with a cogging (12) of the respective step bearing (7). For the purpose of limiting the forces acting in radial direction, the outer surface of each step bearing (7) is kept free. The step bearing (7) is held in radial direction by a shoulder (9) of the threaded bolt (6) (FIG. 2).

The invention refers to a ship propeller, in particular for motor boats,comprising at least two propeller blades. Each blade of which is mountedfor being swivelable around an axis oriented in normal direction to theaxis of the propelling shaft on a propeller star put onto the propellingshaft. For the purpose of effecting such swivelling movement there isprovided an adjusting drive means guided along the propelling shaft.Each propeller blade carries a step bearing rotatably supported on thepropeller star by means of a bolt extending in normal relation relativeto the axis of the propelling shaft and that the propeller blade isconnected with a cogging being in meshing engagement with a cogging ofthe adjusting drive means.

Marine propulsions are most frequently designed as submarine propellers.There are used, with consideration of effectivity and of economy, forbigger ships propeller arrangements operated with sub-cavitativerotating speed, i.e. with a rotating speed being geared down for amultiple relative to the motor speed. On the other hand, there are knownfor rapid racing boats, high-strength racing propellers of great pitchand small diameter and being frequently operated as surface propellerswith the speed of the motor speed, which means that they rotate withsuper-cavitative speed. In this case, optimum operation of such asurface propeller is obtained if it extends below the water surface forhalf of its diameter.

For various reasons, it is frequently desired to be in the position toadjust the propeller blades. This is not accompanied by difficulties incase of ship propellers being operated with sub-cavitative speed. Forthis purpose, there is provided an adjusting propeller hub comprising abipartite housing enclosing the adjusting mechanism and having arelatively great diameter on account of the necessity to bearinglysupport the propeller blades and to accommodate therein the propelleradjusting pinions and the toothed racks being in meshing engagementtherewith. Thus, it becomes impossible to use the known adjustingpropeller constructions for surface propellers, because the centrifugalforces would become too great on account of the high rotating speed ofthese propellers. This equally applies for a ship propeller arrangementof the initially described type U.S. application Ser. No. 2 715 446) inwhich the propeller star carries radial bolts, each of which forms acentering means for its propeller blade being in its interior connectedin a non-rotatable manner with a bevel gear. A housing portion holdingin position the propeller blade against the radially acting centrifugalforces extends between the step bearing and said bevel gear. Such aconstruction can not be used for ship propellers being operated withsuper-cavitative speed.

It is an object of the invention to avoid these drawbacks in such amanner that an adjusting propeller construction can be operated assurface propeller, i.e. with super-cavitative speed (motor speed). Thistask is, according to the invention, solved by the fact that the stepbearing is fixed on the propeller star by the bolt in atension-transmitting manner and that the step bearing carrying thecogging has its outer surface substantially exposed. In this manner,each bolt fulfills the role which has been fulfilled by the housing ofthe previously described known construction, so that this housing isomitted and the outer surface of the step bearing is thus substantiallyexposed. Thus, there results a compact construction, i.e. a constructionin which all component parts required for adjusting the propeller bladesare located as near as possible in proximity of the axis of the driveshaft, which results as compared with the known construction in areduction of the centrifugal forces. On account thereof, it becomespossible to operate the construction according to the invention withsuch a high speed that its use as a surface propeller is possible.

In principle, it would be conceivable to provide the bolt at its bothends with one shoulder each, which provides the tension transmittingconnection between propeller blade and propeller star. It is, however,much more favourable and simple if each bolt is a threaded bolt beingscrewed into a female thread of the propeller star. To be in theposition to make the length of the thread, which has to receive theradially acting tension forces, as long as possible, each step bearinghas, according to the invention, at its inner side a conical surface, bymeans of which it is supported on a conical surface of the propellerstar. This not only results in automatically centering the step bearingon the propeller star but also in the advantage that the circumferentialportion of the step bearings and the portions of the propeller starlocated radially remote from the threaded bolt are brought in closerproximity to the propelling shaft so that the centrifugal forces arereduced. For the latter reason it is also convenient if, according tothe invention, each bolt has at its outer end a shoulder beingcountersunk in a recess of the outer surface of the step bearing. Thissimultaneously results in reliably maintaining in position the stepbearing and in a great bearing surface for rotating the step bearingrelative to the bolt when adjusting the propeller blade. By suitablyselecting the shape and the material of the bolt, maximum admissiblecentrifugal forces of the propeller can be resisted.

According to the invention, each step bearing carries on itscircumference the cogging, which cooperates with the cogging of theadjusting drive means. The construction according to the inventionprovides thus the possibility to give the coggings of the adjustingdrive means cooperating with the coggings of the step bearings maximumdimensions, because the step bearings must not be below a minimumthickness required for receiving the bolts or, respectively, theshoulders thereof.

For the purpose of equalizing the centrifugal forces acting in radialdirection and for the purpose of reducing the flow resistance, the outersurfaces of the step bearings are, according to the invention, given aspherical shape, noting that the shoulder of each bolt is preferablylocated with its outer surface within this spherical surface. Thus, eachstep bearing forms with its outer surface a spherical segment, thediameter of which, which is given the maximum possible size, is limitedby the circumstance that the spherical segments must not come in mutualcontact during the adjusting movement. Within the spirit of theinvention, only such clearance of motion is admitted between thecoggings of the spherical segments formed by the step bearings of thepropeller blades as is required for the mentioned adjusting movement,but the space being at disposal is completely utilized on account ofstrength considerations.

For the purpose of reliably receiving the centrifugal forces, thethreaded bolts must not only be strongly dimensioned with respect totheir diameters, but must also have long threads. According to apreferred ambodiment of the invention, the threaded bolts extend thus tothe driving shaft. For the purpose of preventing any unintendedloosening of the threaded bolts, the threaded bolts are secured inposition by fixing screws in the propeller star.

Further features and advantages of the invention can be derived from thedescription of an example of embodiment being schematically shown in thedrawings.

FIG. 1 shows in a side elevation and partially in a section an adjustingmechanism for a surface propeller.

FIG. 2 shows a vertical section through the propeller hub in a greaterscale.

The propeller arrangement 1 is driven via a drive shaft 2 being designedas a solid shaft and being bearingly supported within a stem tube 3. Apropeller hub 4 carrying the propeller blades 5, four blades in theembodiment shown, is seated on the drive shaft 2. The propeller hub 4has no outer shell receiving the centrifugal forces exerted by thepropeller blades 5, but, to the contrary, all components of the drivemeans required for adjusting the propeller blades 5 are arranged forimmediately surrounding the drive shaft 2, so that the diameter of thehub 4 can be kept very small for the purpose of reducing the centrifugalforces. The propeller blades are fixed in position by means ofhigh-strength threaded bolts 6, which extend through step bearings 7being integral with the propeller blades 5 and which are screwed withlong threads into a propeller star 8 comprising a central bearing andcentering block being rotatably put onto the drive shaft 2.Conveniently, these threads extend to the shaft 2 or to proximitythereof. Each threaded bolt 6 has at its outer end a shoulder 9 ofenlarged diameter, said shoulder being seated within a recess 10 of thestep bearing 7 such that it is flush with the outer surface 11 of thestep bearing 7 and forms therewith a spherical surface (sphericalsegment). Each threaded bolt is secured in position by a fixing screw 34being screwed into the propeller star 8 from its rear side. The stepbearings 7 simultaneously form the adjusting pinions for the propellerblades 5 connected with said step bearings for swivelling the propellerblades around the respective axis of the bolts 6. For this purpose,there is provided on the circumference of each step bearing 7 a cogging12 cooperating with a cogging 13 of two bevel gears 14, 15. The bevelgear 15 located adjacent the free end of the drive shaft 2 isnon-rotatably connected with the drive shaft 2 by means of a wedge 16,whereas the other bevel gear 14 is non-rotatably mounted by means of athread 36 on a hollow shaft 17 surrounding the drive shaft 2 and iscentered by means of a bushing 18. When relatively rotating the driveshaft 2 with respect to the hollow shaft 17, there results, in thismanner, synchronous rotation of all propeller blades 5. For the purposeof increasing the effective length of the thread of the threaded bolts6, the propeller star 8 carries for each propeller blade 5 an outwardlyextending protrusion 19 being lathed at its outer front surface to theshape of a conical surface 20 on which is seated an equally shapedconical surface of the step bearing 7. This simultaneously results incentering the respective step bearing 7 on the propeller star 8. Thisresults in a centered and tilting-stable support for each propellerblade 5 and being capable to resist maximum centrifugal forces acting inlongitudinal direction of the respective bolt 6 as well as to thetilting moment exerted by the propeller thrust. On account of an outermantle being omitted, the step bearings 7 can be given a maximum sizeand the adjusting cogging is provided on the maximum possible outerdiameter of the propeller hub 4 being formed of the component parts6,7,8,14,15, so that said cogging can be given a sturdy size. Theadjusting cogging is flown around by water which is, however, of noimportance on account of the small adjusting movement being effectedonly in rare cases.

A restoring ring 21 can be seated on the free end of the drive shaft 2,said ring being held in position by a disc 22 and a screw 23. Afterloosening the screw 23, the component parts 21,15 and 8 can, togetherwith the component parts 5,6,7, be pulled off the shaft 2 in rearwarddirection. All component parts being moved during the adjusting movementof the propeller are sealed with respect to water by sealing elements,preferably 0-rings 24, so that leakage of the gearing oil used forlubricating the whole propeller head and being circulated between thedrive shaft 2 and the hollow shaft 17 is prevented.

Immediately adjacent the propeller hub 4, there is provided forreceiving the radial forces exerted of both shafts 2,17 a rubber bearing25 being lubricated with water supplied via a conduit 35. The rubberbearing 25 is seated within a supporting tube 26 being maintained inposition within the stem tube 3 by means of supporting ribs 27.Interstices are existing between the supporting ribs 27 and are inconnection with the annular space located between hollow shaft 17 andstem tube 3, said interstices providing the possibility to supply, forthe purpose of improving the effectivity of the propeller mechanism 1,in direction of the arrows 31 to the suction side of the propellerblades 5 effluent gases of the motor, cooling water for the motor andoptionally also pressurized air, which are introduced into the stem tube3 via a connecting piece 28 (FIG. 1). The stem tube 3 is adjustably heldwithin the boat hull 29 for axial adjustment by means of a packing box30 and carries within the interior of the boat the adjusting drive means32 for the relative rotation between hollow shaft 17 and driving shaft 2for the purpose of adjusting the position of the propeller blades. Theadjusting drive means 32 is preferably of mechanical design and has anactuating handle 33.

I claim:
 1. A high speed ship propeller comprising:a propeller shaft having a longitudinal axis; a central bearing and centering block coupled to said propeller shaft for common rotation therewith and having a first conical bearing surface and a threaded bore; at least two propeller blades, each of said propeller blades having(i) a socket means having a second conical bearing surface engageable with said first conical bearing surface for bearing said propeller blade on said central bearing and centering block; (ii) wherein said socket means has a rounded outer surface such that a periphery of said outer surface is disposed nearer said propeller shaft than is a center portion of said rounded outer surface and wherein said rounded outer surface is substantially exposed to a fluid surrounding said propeller blade; (iii) a first cogging; (iv) a threaded bolt to couple said propeller blade to said central bearing and centering block and extending perpendicularly to said longitudinal axis of said propeller shaft, penetrating through said second conical surface, and threaded into said threaded bore of said central bearing and centering block, wherein a shoulder of each of said threaded bolts is flush with the rounded outer surface of said socket means; and a drive means having a second cogging engageable with said first cogging of said propeller blade, for swivelling said propeller blade around a longitudinal axis of said bolt and wherein said longitudinal axis of said bolt is perpendicular to said longitudinal axis of said propeller shaft.
 2. The high speed ship propeller according to claim 1, wherein each of said bolts has a shoulder, located at an outer end of said bolt, countersunk within a recess of the rounded outer surface of said socket means.
 3. The high speed ship propeller Ser. No. 07/353,654 according to claim 1, wherein the first cogging is located on a circumference of said socket means.
 4. The high speed ship propeller according to claim 3, wherein the drive means further comprise bevel gears non-rotatably mounted onto the propeller shaft and onto a hollow shaft surrounding said propeller shaft, and wherein said second cogging is provided on said bevel gears.
 5. The high speed ship propeller according to claim 1 wherein the rounded outer surface of each socket means has a spherical shape.
 6. The high speed ship propeller according to claim 1 wherein the threaded bolts extend substantially to the propeller shaft.
 7. The high speed ship propeller according to claim 1, wherein each of said threaded bolts are secured to said central bearing and centering block by a fixing screw.
 8. The high speed ship propeller according to claim 1 wherein the drive means further comprises a plurality of sealing elements to seal a restoring ring, said bevel gear, said central bearing and centering block, said propeller blades, said threaded bolts and said socket means, actuated by said drive means, from a remaining set of components not moved by said drive means. 